Add onLoad & onLoadEnd callbacks to Prefetch.

Libraries/Pano/Prefetch.js

@@ -52,12 +52,30 @@ const Prefetch = createReactClass({
       // Opaque type returned by require('./image.jpg')
       PropTypes.number,
     ]),
+
+    /**
+     * Option onLoad callback called on success
+     **/
+    onLoad: PropTypes.func,
+
+    /**
+     * Option onLoadEnd callback called on success or failure
+     **/
+    onLoadEnd: PropTypes.func,
   },
 
   getDefaultProps: function() {
     return {};
   },
 
+  _onLoad: function() {
+    this.props.onLoad && this.props.onLoad();
+  },
+
+  _onLoadEnd: function() {
+    this.props.onLoadEnd && this.props.onLoadEnd();
+  },
+
   render: function() {
     const props = {...this.props} || {};
 
@@ -71,7 +89,7 @@ const Prefetch = createReactClass({
     }
 
     return (
-      <RKPrefetch {...props}>
+      <RKPrefetch {...props} onLoad={this._onLoad} onLoadEnd={this._onLoadEnd}>
         {this.props.children}
       </RKPrefetch>
     );

ReactVR/js/Views/Prefetch.js

@@ -52,6 +52,36 @@ export default class RCTPrefetch extends RCTBaseView {
       return;
     }
 
+    const onError = () => {
+      onLoadEnd();
+    };
+
+    const onLoad = texture => {
+      // call onLoad in React
+      if (texture !== undefined) {
+        RCTPrefetch.addToCache(uri, texture);
+        this.UIManager._rnctx.callFunction('RCTEventEmitter', 'receiveEvent', [
+          this.getTag(),
+          'topLoad',
+          [],
+        ]);
+      }
+
+      onLoadEnd();
+    };
+
+    const onLoadEnd = () => {
+      // call onLoadEnd in React
+      this.UIManager._rnctx.callFunction('RCTEventEmitter', 'receiveEvent', [
+        this.getTag(),
+        'topLoadEnd',
+        [],
+      ]);
+    };
+
+    // No progress indication for now.
+    const onProgress = undefined;
+
     if (Array.isArray(uri)) {
       // Cubemap, check proper format
       if (uri.length !== 6 || !uri[0].uri) {
@@ -65,13 +95,13 @@ export default class RCTPrefetch extends RCTBaseView {
 
       const loader = new THREE.CubeTextureLoader();
       loader.setCrossOrigin('Access-Control-Allow-Origin');
-      loader.load(urls, texture => RCTPrefetch.addToCache(uri, texture), () => {}, () => {});
+      loader.load(urls, onLoad, onProgress, onError);
     } else {
       // Panorama
       const url = RCTPrefetch.getUri(uri);
       const loader = new THREE.TextureLoader();
       loader.setCrossOrigin('Access-Control-Allow-Origin');
-      loader.load(url, texture => RCTPrefetch.addToCache(uri, texture), () => {}, () => {});
+      loader.load(url, onLoad, onProgress, onError);
     }
   }